These questions relate to the reading assignments.  Brief answers are fine.

(1) How to hear a hummingbird in a hurricane (Fisher)

Key idea: in an environment with poor signal-to-noise, you can improve the detectability of a weak signal by modulating it and synchronously detecting the modulated signal with a phase-sensitive amplifier.

Question: how do modulation and phase-sensitive detection improve signal-to-noise?

(2) Unified approach to measurand reconstruction (Morawski)

Key idea: it is useful to step up a level from specific measurement applications to view all measurements as instances of a general model-inversion problem.

Question: None.  This reading was intended to illustrate the flavor of what formal measurement theorists do.  

(3) Metrology: quo vadis? (Kind ++)

Key idea: metrology standards have evolved from artifacts to recipes for robust experiments; isolated national standards labs have evolved into an
integrated international network.

Question: why has the discovery of "macroscopic quantum effects" (like the Josephson Effect and the Quantum Hall Effect") made it possible to abandon artifact-based standards?

(4) Compact transportable Josephson voltage standard (Hamilton ++)

Key idea: A portable voltage standard has been developed based on the Josephson effect.

Question: This apparatus is outwardly very complex compared with previous
voltage standards, which were really just very pampered batteries.  Why is it
in fact much better and, in a fundamental sense, actually simpler? 

(5) Effect of impedance mismatching and time delays in ultrasonic measurement (Eren)

Key idea: ultrasonic transit time is a useful way to measure liquid flow through pipes, etc, but the measurements are subject to many perturbations.

Question: identify a perturbation that results in an impedance mismatch and
a perturbation that results in a time delay.

(6) Thermodynamic constraints on relectance reciprocity and Kirchoff's law (Snyder ++)

Key idea: it is generally argued on thermodynamic grounds that the "bidirectional reflectance distribution function" (BRDF) describing a
surface is the unchanged when source and detector are exchanged; the authors conclude that the thermodynamic argument is flawed, but that the principle is nevertheless true for typical surfaces.

Question: sketch the geometrical arrangement of source, reflecting surface,
and detector that show in what sense the BRDF is "bidirectional". Contrast it to the Snell's Law reflection function. 

(7) Single Lens Stereo with a Plenoptic Camera (Adelson ++)

Key idea: by placing an array of lenslets, each the size of, say, a 3x3 array
of pixels, over a camera sensor, it is possible to capture the three dimensional structure of a scene with a single-lens camera.

Question: To reconstruct stereo you need both ray intensities and ray angles.  What price must you pay for the information about ray angles that this camera captures but that ordinary cameras discards?

(8) Low level light detectors in astronomy (Eccles) [Introduction]

Key idea: survey the origins and issues of signal, noise, and resolution at very low light levels.

Question: A CCD cell is "full" when it contains 500,000 electrons, at which point it's output is 5.0 volts.  A star's image formed by a telescope on one pixel of this CCD results in a signal level of 0.1 volts.  The sensor is cooled to a low temperature so it can be operated at a low frame rate: 1 frame per 1000 seconds.  The quantum efficiency of the CCD is 10%.  Why does cooling the CCD help? How many photons/sec are reaching the pixel?  What frame-to-frame statistical fluctuation would you expect in this number?

(9) Image tubes (Csorba) [Photometric Quantities]

Key idea: survey the lambertian radiator, image brightness and uniformity, radiometric and photometric definitions, conversion between them, quantum efficiency, black body radiation, and tristimulus color perception.

Question: why do we have parallel systems of "radiometric" and "photometric" units for measuring quantities relating to illumination?

(10) In situ calibration for quantitative ultrasonic imaging (Siegel ++)

Key idea: by measuring time-of-flight over multiple acoustic paths it is possible to make accurate tissue layer thickness measurements even when the speed of sound in these layers is uncertain.

Question:  a transmitter and a receiver are placed 20 mm apart on the skin,
and a time-of-flight of 36 microseconds is measured.  The transducers are then placed 40 mm apart and a time-of-flight of 42 microseconds is measured.  Estimate the layer thickness and the speed of sound in it.

(11) Physically based simulation model for acoustic sensor robot navigation (Kuc ++)

Key idea: previously unexplained anomalies in sonar range maps of interior environments could be precisely understood via a model based on specular reflection, acoustic beam width, and the commonly-used threshold-based approach to time-of-flight measurement.

Question:  How can analysis of sonar signals distinguish walls from corners from edges?  Why is the range map from a mobile robot to a wall a circular arc that is tangent to the wall rather than a straight line coincident with the wall? 

(12) http://www.boulder.nist.gov/timefreq/

Key idea: gateway to information about time and frequency standards and dissemination by NIST.

Question: after (14).

(13) http://www.utexas.edu/depts/grg/gcraft/notes/gps/gps.html

Key idea:  Overview of the Global Positioning System architecture.

Question: after (14).

(14a) http://www.metaresearch.org/mrb/gsp-relativity.htm OR
(14b) http://vishnu.nirvana.phys.psu.edu/mog/mog9/node9.html

Key idea: special and general relativity cause clocks in satellites to run at different rates from clocks on the ground; the differences are big enough that they must be taken into account in GPS calculations.

Question: Why does it require at least four satellites in view to obtain a three dimensional position fix?  What are "differential GPS" and "differential carrier-phase GPS"?  In what sense is the CDMA coding scheme that is used for the GPS message similar to the synchronous detection method of Question 1?